1. Field of the Invention
The invention relates to a method and apparatus for ascertaining tool path contours by means of numerically controlled machines, and particularly to tool path contours created from corrected base bodies united to form a corrected workpiece and to tool paths machining workpieces involving staggered depth layers.
2. Description of the Prior Art
In numerically controlled (NC) machine tools, data is determined for producing a workpiece from a workpiece blank in the form of tool path data by means of an NC program. This requires correcting the contour of the workpiece to be produced with the tool radius, since it is not the workpiece contour but rather the center point of the tool path that is relevant to the machine in producing the workpiece.
For NC control, calculating the corrected sectional contour of a given body is a complex task requiring a great deal of calculation. Difficulties reside in defining a complex body and its surface and in calculating an equal distance for the cutter radius correction, taking possible collisions into account with a given accuracy. The amount of computer capacity and memory capacity needed is correspondingly high. To perform such calculations, additional hardware and software are necessary on the NC control computer. These include special arithmetic processors, for instance, as well as geometric methods and display methods for describing free-form surfaces.
It is known that relatively complex body contours can be constructed from simple contour parts such as circles and rectilinear lines. The tool radius corrections can be carried out easily with these simple contours, however, it becomes problematic to ascertain the resultant tool path from the various corrected contours constructed to form the complex body, since overlapping occurs when the various corrected contours are put together. Specifically, the tool path contours determined by the corrected path data do not necessarily coincide with the intersection lines of the assembled contour parts.
Accordingly, an object of the invention is to ascertain the allowable peripheral points for an arbitrarily composed contour, the sequence of which points corresponds to the tool path that the contour of the workpiece generates.
The advantages of this method and apparatus are that for a complex contour, the necessary cutter path data can be obtained in a simple manner from the ascertained allowable peripheral points.
Further objects and advantages will become apparent from the following description and the accompanying drawings.